Veterinary Services

Two Suffolk ram lambs from an Aberdeenshire holding were submitted from a group of 35 weaned lambs grazing a field of typhon - a cabbage-turnip hybrid used as a fodder crop.  In addition the group had ad lib access to concentrate pellets. The history indicated that when these pellets ran out the hoppers were not replenished for some 48 hours.  In the 24 hours immediately following the refilling of the hoppers a total of five lambs were found dead.  The gross postmortem changes and rumen pH  in both carcases were consistent with rumen acidosis due to a concentrate overload.

Parasitic diseases

Chronic fasciolosis and parasitic gastroenteritis were confirmed in an Inverdale ewe submitted to Aberdeen. The owner reported 21 ewe and gimmer deaths since January and generalised ill thrift across the whole flock.  The history indicated a single prophylactic treatment for liver fluke some six months previously.

For much of Scotland, May is when significant outbreaks of nematodirosis are recognised for the first time.  This year the problem appeared to be less severe, with a total of 19 outbreaks recorded, compared to 45 over the same period last year. SAC VS suggest that such variations depend on temperature and its effect on the hatching of infective third stage larvae (L3) of Nematodirus battus, and subsequent consumption by young lambs. 

In one outbreak a two-month-old Texel lamb collapsed and died when gathered.  The carcase was dehydrated and a profuse scour was evident. Some 11,800 Nematodirus spp worms were counted in an intestinal wash. A two-month-old Suffolk lamb was submitted as a sudden death from a second farm.  The burden of N. battus worms in this case was uncountable.  The kidneys were friable and haemorrhagic and epsilon toxin was detected in the intestinal contents, suggesting concurrent pulpy kidney disease.

Coccidiosis was diagnosed in a crossbred lamb found dead on an Aberdeenshire holding. Several other deaths were reported in the group, treated with avermectin one week previously.  A faecal coccidial oocyst count of 13,800 oocysts per gram was recorded. Speciation confirmed that 100 percent of these were Eimeria crandallis, a pathogenic species.

Generalised and systemic conditions

The fourth and fifth Scottish blackface lambs to develop similar clinical signs in the same group were submitted to Dumfries.  In all cases the lambs were seven to ten days of age and were found recumbent with painful, slightly swollen abdomens.  They died despite antibiotic treatment.  At postmortem examination the abomasa were distended with a mixture of milk and mucus, and showed mucosal petechiation.  The kidneys were very pale and swollen in one case.  There was no evidence of scour.  Clostridium sordellii was identified by the fluorescent antibody test (FAT) and culture; however histopathology showed no evidence of an abomasitis.  As the lambs were submitted alive and euthanased, SAC VS considered the C. sordellii isolate could not represent a postmortem invader.  Histopathology confirmed nephrosis in both cases and the intestinal contents of one lamb were also positive for epsilon toxin of C. perfringens.  SAC VS speculated that production of enterotoxin may have resulted in gut stasis, allowing both toxin absorption and the overgrowth of C. sordellii. 

Alimentary tract disorders

Necrotic abomasitis associated with C. sordellii and C. septicum infection was evident in a thriving pedigree Texel lamb, one of two which died suddenly on an Ayrshire farm.  The dams had been given a clostridial vaccine prior to lambing. However the farmer suspected that an additional risk factor may have been soil ingestion associated with mole activity in the field where the lambs were grazing.

Respiratory tract conditions

Ovine pulmonary adenocarcinoma (OPA) was suspected on gross examination of a three-year-old mule cross ewe found dead. OPA was confirmed on histopathological examination. There was secondary infection with Mannheimia haemolytica.  The farm reported four deaths in adult ewes which lambed approximately six weeks previously.

Atypical pneumonia due to infection with Mycoplasma ovipneumoniae was suspected grossly and by histopathology in a five-month-old Charollais lamb, although M ovipneumoniae was not isolated.  Eight deaths and a morbidity of 50 per cent were reported in a group of 80 lambs, which developed a dry cough whilst housed in a polytunnel. Secondary infection with Mannheimia haemolytica and Pasteurella multocida was confirmed.

Reproductive tract conditions

This year the owners of 412 sheep flocks submitted foetal material to their local SAC VS centre to assist in the investigation of an abortion outbreak.  This compared to 401 flocks over the same period in 2008. 

Each spring, a dozen or more different infectious agents are recorded as the cause of these outbreaks.  This year, the two most common diagnoses in Scottish flocks remained  enzootic abortion of ewes (EAE) caused by Chlamydophila abortus infection and toxoplasmosis (figure 3 - see top right-hand side). Together they accounted for almost 60 per cent of the diagnosed sheep abortion outbreaks in 2009. This is slightly more than the equivalent figure for 2008.

 
Other common causes of abortion included the bacterial organisms Campylobacter, Listeria and Salmonella.   The "Other" category, was responsible for more than 20 percent of outbreaks where a diagnosis was made. This includes a number of pathogens encountered more sporadically, including border disease virus and bacteria such as Arcanobacterium pyogenes, Bacillus licheniformis, Yersinia, Staphylococcus and Streptococcus species. 

Inverness reported sporadic abortions on two separate farms attributed to Streptococcus uberis and Streptococcus pluranimalium.  Although known as a cause of bovine abortion, this was the first instance that Streptococcus pluranimalium has been isolated from ovine abortion material in the area.  Thurso also reported abortions in ewes due to salmonellosis in four separate flocks. In each case the organism responsible was Salmonella Montevideo.

Musculo-Skeletal conditions

Dumfries recorded three cases of hoggs returning from wintering with stiff joints and bowed legs in some cases.  The carcases of two 11-month-old Scottish blackface hoggs were submitted from one farm for postmortem examination.  They were in average body condition and showed an obvious carpal valgus in one case.  At necropsy, widening of the epiphyseal growth plates was evident in the femur and humerus (figure 4 - see top right-hand side).  The total serum vitamin D was below detectable limits in one animal and 5.0 nmol/l in the other (in humans, levels below 12.5 nmol/l are regarded as indicative of severe deficiency).  These results confirmed the suspected diagnosis of rickets. 

Outbreaks of suppurative polyarthritis due to infection with Streptococcus dysgalactiae were confirmed on six occasions this month.  In one case, the outbreak included the detection of a spinal abscess in a two-week-old crossbred lamb, as well as the more typical signs of joint ill.

Nervous system disorders

Swayback was diagnosed in a two-day-old Cheviot lamb from an Ayrshire flock. Ten lambs were reported to be unsteady from birth, unable to stand and suck, and three affected lambs died within a few days. The diagnosis was confirmed following the observation of typical neuropathological lesions in the brain and spinal cord, including demyelination.  The liver copper value was well below the minimum value of the reference range.  Hypocupraemia was evident on examination of blood samples from other ewes with affected lambs and advice was provided on copper supplementation.

Blood samples were received from a Scottish Borders flock where more than thirty ewe replacements died in the previous month.  Although the majority were found dead, a number showed convulsions prior to death.  These ewes were wintered away from home and on returning to the holding picked up a heavy tick burden. Serology confirmed recent infection by louping ill virus and exposure to the agent of tick borne fever.